A device of this kind is known from WO 02/30661 to the applicant of the present invention. This reference discloses the use of teeth whose geometrical shape and/or surface deviates from which of the satinizing teeth in order to produce signs with optical effects depending on the viewing position and/or the light source, thereby allowing to produce security features which are very difficult to copy. While the disclosed geometrical deviations of the tooth shapes and height are all comprised in the macroscopic range of 30 to 100  (micrometers), no details are specified with regard to the surface design of the teeth and of the tooth space bottom.
WO 02/076716 to the same applicant discloses devices for the treatment of flat materials in which an embossing roll provided with individual teeth cooperates either with a second mating roll provided with the same toothing and with a mating roll having no individual teeth, or only with a roll having no individual teeth. This allows to achieve particularly precise embossing operations for the above-described effects.
The device for satinizing a foil described in EP-B-925 911 to the applicant of the present invention, which is based on the knowledge from earlier patents of the same applicant, comprises two rolls which are arranged in a mutually displaceable manner such that a self-stabilizing effect results when the teeth of the rolls interpenetrate, thereby providing a high processing speed, on one hand, and a high precision, on the other hand. First of all, this allows a uniform satinizing operation, and with a corresponding machining of the teeth, a highly precise embossing of foils.
EP-A2-0 194 042 discloses an embossed object on the substrate of which first and second optically non-diffractive relief elements defining first and second patterns are embossed, the patterns having a uniform reflectivity and their appearance varying with the viewing angle. The specification discloses line patterns only, and no satinizing is intended.